The use of AEROSIL® fumed silica as an anti-settling agent for pigments and fillers in liquid systems is widely spread through different applications (e.g. paints, coatings, toothpastes, repair-putties, colored gel coats etc.).
Already small amounts of AEROSIL® fumed silica may prevent large quantities of pigments and fillers from settling down under the influence of gravity. Depending on the kind of system AEROSIL® fumed silica is added in the range of 0.5 to 5 percent by weight. In colored gel coats for example, the silica concentration is already around 2.0 percent due to the required thickening effect.
To use AEROSIL® fumed silica as an effective anti-settling agent a good dispersion is required. Well dispersed fumed silica provides better anti-settling properties (see TI 1279: Successful Use of AEROSIL® Fumed Silica in Liquid Systems).
For non-polar systems usually AEROSIL® 200 is recommended as in most cases a thickening effect is required as well.
If AEROSIL® fumed silica is only needed for the anti-settling effect, often AEROSIL® R 972 is used. It will have less thickening effect in non-polar systems.
When the base fluid of the dispersion is more polar (e.g. vinyl ester resin), it is recommended to try hydrophobic AEROSIL® fumed silica grades, such as AEROSIL® R 202 and AEROSIL® R 812.